U.S. Pat. No. 5,058,549 describes a fuel injector that has a device for producing swirl, as well as main injection opening having a large diameter and a secondary injection opening having a smaller diameter. The inclination of the injection openings in relation to a longitudinal axis of the fuel injector differs, so that the fuel is injected through the secondary injection opening with a high degree of swirl and a large penetration length, and is injected through the main injection opening with a low degree of swirl and with a large opening angle.
One disadvantage of the fuel injector described in U.S. Pat. No. 5,058,549 may be, in particular, the high manufacturing expense both of the valve-closure member and/or of the valve needle, which must be provided with swirl grooves, and also of the valve-seat member, in which the injection openings are formed. In particular, the differing inclination of the injection openings and the high demands on the precision of the diameter of the injection openings require an expensive manufacturing process.
In addition, German Patent No. 1 601 988 describes a fuel injector having a valve needle whose shaft is guided in the bored opening of a valve guide part. When fuel under pressure is supplied, the fuel injector opens in the direction of flow of the fuel via radial cross-bores that are situated in the guide part and that run into the guide bore, and places the fuel into rotation using grooves. In addition, the fuel injector has at least two injection openings at the flow-off side of the valve needle.
One disadvantage of the fuel injector described in German Patent No. 1 601 988, in particular, the disturbance of the swirl of the fuel due to the outwardly directed opening motion, caused especially by the large dead volume of a swirl chamber formed between the valve-closure member and the injection openings. The swirl flow can no longer be kept homogenous, and when the fuel injector is opened the cross-section of the grooves increases so strongly that the swirl flow ceases.